1. Technical Field
The present invention relates to a liquid ejecting head in which liquid droplets are ejected from a nozzle by deforming a piezoelectric element and a liquid ejecting apparatus, and more particularly, a structure of an actuator including the piezoelectric element.
2. Related Art
In the related art, a liquid ejecting head has been disclosed, in which liquid droplets are ejected from a nozzle communicating with a pressure generation chamber by deforming a piezoelectric element (an actuator) and then by generating a pressure change in the liquid inside a pressure generation chamber. A representative example thereof is an ink jet type recording head ejecting ink droplets as the liquid droplets.
The ink jet type recording head includes, for example, the piezoelectric element on one side of a flow path formation substrate in which the pressure generation chamber communicating with the nozzle is provided, and the ink droplets are ejected from the nozzle by deforming a vibration plate by the driving of the piezoelectric element and then by generating the pressure change in the pressure generation chamber.
Here, the piezoelectric element is configured to include a first electrode, a piezoelectric layer and a second electrode which are provided on the vibration plate, and there is a problem that the piezoelectric layer may be easily destroyed, for example, due to the external environment such as moisture. In order to solve the problem, there has been a technique in which an outer periphery section of the piezoelectric layer is covered by the second electrode. For example, there has been a technique in which an individual electrode is formed by providing the first electrode for each pressure generation chamber and a common electrode is formed by continuously providing the second electrode throughout a plurality of the pressure generation chambers, and the outer periphery section of the piezoelectric layer is covered by the second electrode (see, for example, JP-A-2009-172878).
Destruction of the piezoelectric layer can be suppressed by covering the piezoelectric layer with the second electrode that is the common electrode as disclosed in JP-A-2009-172878.
However, in the piezoelectric element having such a configuration, stress concentration occurs at a boundary between a portion (an active portion) in which a piezoelectric strain occurs on the piezoelectric layer and a portion (a non-active portion) in which the piezoelectric strain does not occur when a voltage is applied between the first electrode and the second electrode.
In addition, in the configuration in which the first electrode, the piezoelectric layer and the second electrode configuring the piezoelectric element are extended to the outside of the pressure generation chamber, large stress concentration occurs further at an end portion of the pressure generation chamber that is a boundary between a portion (a flexible portion) facing the pressure generation chamber and a portion (a non-flexible portion) of the outside of the pressure generation chamber in the portion (the active portion) in which the piezoelectric strain occurs on the piezoelectric layer. Accordingly, there is a concern that burning, cracks or the like may occur.
In addition, there is a problem that since the second electrode is formed relatively thin, the resistance is great and reduction of liquid ejection characteristics or variation (a so-called electric crosstalk) is likely to occur due to the voltage drop.
In addition, such a problem also exists similarly in the liquid ejecting head ejecting the liquid besides the ink as well as in the ink jet type recording head.